Electric furnace.



S. H. FL-EMING.

ELECTRIC FUHNAC.`

APPLICATION FILED MN. 1, |914.

l Patented Ju1y25, 1916.

2 SHEETS-SHEET l.

lnllvll AVIII w/ TNESSES X'. 'KM

yuf Ang' UNITED sTATEs PATENT OEEICE.

smoEL H. ELEMING, or CLEVELAND, OHIO, AssIGNoE'r'o NATIONAL 'CARBON COMEANY, OE CLEVELAND, OHIO, A CORPORATION OE NEW JERSEY.

ELECTRIC FURNACE.

I To all whom it may concern' Be it known that I, SAMUEL H. FLEMiNG, a citizen of the United States, residing at Cleveland, in the county of Cuyahoga and In the kelectric calcination, or other treatment of coke, or other carbonaceous material, it frequently ha pens that the carbon is heated to a much iiigher temperature at certain placesl than at others. Since carbon has a negative co-efticient of resistance, the currentwill be diverted fromA the cooler portions and concentrated in the path through the material more highly heated. yIn this way, one portion of the material may rob the remainder of substantially all the current.

verge the moving material toward the point where the electric heat is applied. so that it all must pass through a constricted area and be uniformly heated.

It has been impossible to calcine or otherwise treat rawcoke and coals, by sending the current through them,"as-such materials are substantially non-conducting to the electric current.

It is another object of my invention to provide an arrangement and method wherevby this can be readily done.

It is known that material can be heated to moderately high tem eratures more economically by gas than y the electric cur-` rent, and ingraphitizing carbon, or in calcining it` to very high temperatures, itis more economical to first ree by means of gas, or by urning part of it, and then to heat it by the electric current to the higher desired temperature.

It is a further object vof my invention to provide an arrangement whereby such. pre-heating of the material can be advantageously carried out. 55.

In .electric furnaces for heating calcined` It is one object of my invention to con-4 at the carbon specification of Letters rama. patented July 25, 1916,A Application mea January 7, 191'4. serial No. s107320. y i

In my electric furnace, -which has the 'ad-A coke, it has been found that earbonaceous vantages previously set forth, thearrangement is'such that substantially no growths of carbonaccumulate on the electrode ends. vThe obJ'ects of the invention lhave `been chiefly .set forth above, but other objects will appear in the appended description taken in 'connection with the drawings, in which:

Figure 1 isa vertical cross sectionv through the center -of the furnace. Fig. 2 is a top view of the furnace roof and flue for the removal of combustion gases. Fig. 3 is an ele-v vation of the upperpart of the furnace looking along the line B-B of Fig.-2. Fig. 4 is at.p view of the arch with the flue for reeis-l,

moving the combustion gases removed, so

that certain portions oflthe furnace are l broughtin view. 5 is a horizontal cross section taken on therline A-A of Fig. 1. Fig. 6 is a vertical cross section taken on the diagonal line B--B of Fig. 2. Y

Referring in detail to the drawings, the outer walls of the furnace designated by reference character 1, are built in the .form of a vertical shaft Vof fire brick or other suitable heat insulating material. As shown inthe drawings, the inclosing walls are` in the form of a square thoughthey may be circularor Aof other form, as the shape is immaterial as far as the invention is concerned. The .base

of the furnace shaft consists of the floor '2 of suitable materiahand the upper. portion is covered by a removable arch 3 of refractory material, held together by structural steel members 5 and 6.'

As shown in Figs. 1 and 3, the arch has a cylindrical curvature, the ends being closed' by brickwork 6 which rests `upon the top portion of the lfurnace walls. A flue 9 consisting of two spaced rings 7 and 8, and a cover plate 10 is built on 'top' of the arch. The cover plate has a central opening 11 for admitting the upper electrode as well as for `the Vcombustion gases are removed.

4 [The combustion gases are admitted to the 9s ioo feeding the furnace charge into the upper sired to get at the interior of the upper part,

of the furnace without removing the entire arch.

The-ring 8 is beveled as shown, to provide a hopper 15 for the material fed into the furnace, and this hopper may be filled through a pipe 16. An electrode 17, which is preferably tapered near the end, extends through the material in the hopper and the opening I8 formed in the centerof the arch, the latter opening being sufficiently larger than the electrode to permit the charge to be fed around it into the top of the furnace.

A partition`19 shown as a crown in the drawing, separates the furnace heating region in tog two chambers' 2O and 21, one being for the pre-heating of the material, and the other for its final heating by the electric current. The crown' is illustrated as being dome shaped, which is preferred. on account of strength, though it may be of other form without departing from the spirit of the invention. Since the body of the furnace as shown, is rectangular in cross section, the corners between the walls and the crown are filled with material such as fire brick 22, for example. (Fig. 6.)

The crown 19 has an opening 23 to permit the passage of the upper electrode 17. A trammel 24 serves to key the brickwork of the dome. The crown 19 has a plurality of openings 25, arranged substantially at an equal distance from the center of the furnace, near where it joins the furnace walls. In Fig. 1 the openings shown in cross section are filled with material, but forpurposes of illustration, the remainder, although similarly Iilled, are not thus shown. Upwardly extending members 2G are placed in the four corners just outside the adjacent openings 25 to prevent the material from clogging the inner air opening 30.

Vithin each of the four walls 1, around the chamber 20, is a channel 28 for preheating air which is admitted to the chamber for the combustion of the gases. The air is drawn in at openings 29 near the corners of the furnace, as shown in Fig. 5, and passes into the combustion chamber 20 at four openings 30, after traversing the channels in the walls. To secure a more tortuous path, projections 31 and 32 extend .into the air channel from the top and bottom respectively. The lower electrode may consist of a plurality of electrodes 33 which extend through the furnace walls. The elec- A plurality of larger openingsl 14 trodes 33, of which four are shown, fit into a channel 34 which is preferably constructed of graphite, on account of its electrical conductivity, and high refractory properties. The electrode being circular in section, the ends are cut to a rectangular shape to more easily fit in with the graphite bricks or vslabs of which the channel 34 is made. The

treated material is removed at the base of the furnace by conveyer 35 after it has been cooled by the water pipes 34. The operation of the furnace is as follows: The granular carbonaceous material. coming through the pipe 16, is admitted to the chamber 20 through the annular passage 1.8, around the electrode' 17. The furnace may be placed in initial operation by feeding thecharge through the hopper until the crown 19 is covered by a cone ofthe material, the base of which is prevented from spreading beyond certain limits by the exterior Walls 1 and the annular pieces 26, as shown in Fig. 5. -When this cone of material has been formed, the lower chamber 21 will be filled by the charge falling through the openings 25 in the crown. This material, of course, will fill up the space between the -channel 34 and the outer Walls as well as the channel itself, until it assumes the form shown in Fig. l. The mate' rial outside of the channel remains in the furnace. When the furnace is filled to this extent, no further material will fall through the hopper 15 and the charge` will be at rest until the furnace is put in full opera tion by starting the conveyer 35.

The surface of the cone in chamber 20, as well as that of the inverted cone in chamber 21, will assume the angle of repose, that is, the angle of friction of granular coke on itself. lVith this condition of affairs, a slight addition of material at the top causes material to slide down the surface.

It is-preferable to'initially start the furnace with calcined coke, and when the electric current is sent through the material, it

will become intensely hot in lthe. region of the top part of the channel 34. Calcined coke, that is, coke calcined by means other than the electric current, still has considerable volatile matter, und this will be driven off by the intense heat and pass up through the interstices of the coke, through the openings 25, and will burn at the base of the upf. per cone on meeting the air in chamber 20. Then by withdrawing the charge at the base of the channel 34, and feeding in a constantly increasing proportion of raw coke, the upper cone will be soon raised to a high temperature, due to the volatile mattei' driven off from the raw coke, which is burned on meeting the air coming through the tortuous channel 28. As soon as the feeding of calcined coke is discontinued and gases given off from it. By the time it reaches the base of the cone, it is thoroughly pre-heated and passes through the openings 25 in the'A crown 19. The moving layer of pre-heated coke then slowly moves along the interior surface of the hollow cone until it converges to the electrode 17, where it passes downward through the channel 34 after being raised to the desired heat bythe electric current.

'On' briefly summarizing the operation, it will be seen that the conveyer 35 at the base of the channel, will remove the treated material and cause a thin stream to move slowly down the diverging conical surfaceof chamber 20, then alongl vthe converging conical surface in cham-ber 21, toward and past the electrode end, and finally down through the channel34. In this way, the combustible gases in the coke are burned along the surface 'of the upper cone by the addition of preheated air. Since the material moves slowly in a thin layer, it is raised. to a high temperature and is evenly heated :by the time it ieaches the openings in the crown. The combustiblefgases are therefore, substantially'all driven ofland coI 1'.

sumed before the material passes through the openings 2 5 in the crown. Since it is impossible to entirely drive off combustible gases by heat treatment, there is always a small quantity of gas given off from the coke at the electric heating region, but this is not sufficient to deposit any material amount of carbon on the electrode, and as there is a slightly .reducing atmosphere under the crown, there is slow consumption of the electrode. Since all of the material converges at the electrode end, and moves in a' narrow path in the electric heating region, the material is very uniformly heated.

In this type of furnace the expense is not only reduced by the'use of-the cheaper raw coke, but also by the pre-heating due to the burning of combustible gases contained therein. It hasA beenfoundthat the preheating of the coke in'my` type of furnace itself reduces the cost of electrical energy from 25 to 50%.

While I have disclosed a resistor ltype of 'furnace that embodies my invention, it is 4, permissible to use other types, and there are also various changes that can be made without departing from the spirit of the 1nvention. The invention is therefore, to be limited only by the appended claims.

Having described my invegtion what I claimis:

-1. In electric furnaces, inclosingwalls', a cover coperating with the said walls to form an inclosureand having a central opening, a partition in'the interior of the furnace dividing it into two chambers, said partition having a plurality vof openings near its junction point with the .walls and a `central opening in line with the opening in the cover, means for admitting air to the upper chamber, an electrode extending through the said central openings and a second electrode coperating with the first electrode to produce electric heat beneath. said partition. I

2. In electric furnaces, inclosing walls, a cover coperating with said walls to form an `inclosure and having an opening for admitting a charge to be heated, a partition in the interior ,of the furnace dividing it into an upper and a lower chamber, said partition having a plurality of openings near itsv junction point with the walls to permit the passage of the charge from the-upper to the lower chamber and gaseous products from the lower. to the upper chamber, means .for admitting air to the upper chamber, means for removing the gaseous products from the 1 upper chamber and means for .introducing electric heat into said charge beneath the partition. I

3. In electric furnaces, inclosing Walls, a

susl

vertical electrode, a' cover coperating with y said walls to f orm an inclosure and having an. opening for admitting said electrode and a surrounding charge, a partition in the interior of the furnace charge supporting the entering charge and having an opening for the passage of the electrode therethrough and a plurality of openings for the passage of the charge and means for passing an electric current through the electrode and the charge beneath said partition.

4. In electric furnaces, inclosing walls, a` cover coperating with said walls to form an inclosure and havingan opening for admitting a charge, la partition in the interior of the furnace dividing it 'into an upper. and a lower chamber and having openingsl for permitting the passage of the charge, an

opening "for admitting air to the upper chamber to burn the gaseous products therein, and means surrounding said upper chamber to preheat the air.`

` I 5. The method of heatingA material capalayer, whereby lit is heated, moving the heated material from the base of said s urface passing it to an electric heating region,

below the slanting surface and removing it after passing through said region.

6. The method of heating granular ma.- terial which consists in causing it to slide as a thin la yer making an angle with the horizontal equal to the angle of repose of said material, burning a combustible mixture in proximity to said layer whereby it is hea'ted, passing it into an electric heating region, and removing it after passing through said region. Y

7. The method of heating granular material which consists in causing it to slide as a thin layer making an angle with the horizontal equal to the angle of repose of said material, burning a combustible mixture invproximity to said layer `whereby it is heated, causing the material to slide in a reversed direction as a thin layer making an angle with the horizontal equal to the angle of repose of said material with an electric heating region, and removing it after passing through said region.

8. The method of heating material capableef giving ofi' combustible gases, which consists in causing it to slide as a thin layer making an angle with the horizontal equal to the angle of repose of said material, iiitroducing air to burn the gases given `off from the material-in said layer whereby it is heated, causing the material to slide in a reverse direction, as a thin layer, making an angle with the horizontal equal to the angle of repose of said'material, into an electric heating region, and removing it after passing through said region.

9. The method of heating material capable of giving 'off combustible gases, which consists in causing it to pass in a-thin layer down a slanting surface, making an angle 'surface and passing it into an electric heati ing region belowthe slanting surface.

10. The method of heating material, ca-

pable of giving oii combustible gases, which consists in passing it in thin layers down diverging surfaces, introducing air to burn the gases given off from material in said layers whereby it is heated, moving the heated material from the bottom of said diverging surfaces and passing it down converging surfaces, and heating it by the electric current 'at or below the converging point.

1l. The method of heating material, capable of giving off combustible 'gases which consists in passing it in a thin layer down a conical surface, introducing air to burn the gases given ofi' from the material in said layer, whereby it is heated, moving the heated material from the base of the cone, and passing it down a converging conical surface, and heating it by the electric current-at or below the apex of said converging surface.

In testimony whereof, I hereunto affix my signature.

SAMUEL H. FLEMING.

Witnesses U. K. MoULToN, H. G. Gnovnn. 

